Monosubstituted aluminum dihalide catalysts for olefin polymerization



United States Patent 3,088,942 MONOSUBSTITUTED ALUMINUM DIHAMDE CAT-ALYSTS F03 OLEFIN PGLYMERIZATKGN Harry W. Coover, .lhx, Kingsport, Tenn,assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of NewJersey No Drawing. Filed Mar. 31, 1958, Ser. No. 724,911 14 Ciaims. (Cl.260--93.7)

This invention relates to a new and improved polymerization process andis particularly concerned with the use of a novel catalyst combinationfor preparing high molecular weight solid polyolefins, such aspolypropylene, of high density and crystallinity. In a particular aspectthe invention is concerned with the preparation of polypropylene andhigher polyolefins having a high density using a particular catalystcombination which has unexpected catalytic activity and which givesproducts characterized by unusually high crystallinity, softening point,thermal stability, stiffness and being substantially free ofnon-crystalline polymers.

Polyethylene has heretofore been prepared by high pressure processes togive relatively flexible polymers having a rather high degree of chainbranching and a density considerably lower than the theoretical density.Thus, pressures of the order of 500 atmospheres or more and usually ofthe order of 10004500 atmospheres are commonly employed. It has beenfound that more dense polyethylenes can be produced by certain catalystcombinations to give polymers which have very little chain branching anda high degree of crystallinity. The exact reason why certain catalystcombinations give these highly dense and highly crystalline polymers isnot readily understood. Furthermore, the activity of the catalystsordinarily depends upon certain specific catalyst combinations, and theresults are ordinarily highly unpredictable, since relatively minorchanges in the catalyst combination often lead to liquid polymers ratherthan the desired solid polymers.

Certain of the trialkyl aluminum compounds havebeen used in conjunctionwith inorganic halides to give high molecular weight polyethylene. Thus,triethyl aluminum in conjunction with titanium tetrachloride permits alow temperature, low pressure polymerization of ethylene to highlycrystalline product. When this same aluminum triethyl is used inconjunction with a titanium tetraalkoxide, such as titaniumtetrabutoxide, the mixture does not produce solid polyethylene for somereason which is not apparent. A mixture of an alkyl aluminum dihalideand a titanium tetraalkoxide can be used to polymerize ethylene to formhigh density crystalline polymers, but when this catalyst is used topolymerize propylene and higher monoolefins high yields of polymericoils and rubber are produced.

When a solid polyolefin of high density and high crystallinity isdesired, a catalyst mixture that produces large quantities of oils andrubber is undesirable and in some instances commercially inadequate.

This invention is concerned with and has for an object the provision ofimproved processes whereby a-monoolefins and particularly propylene canbe readily polymerized by catalytic means to give high molecular weight,highly crystalline polymers. A particular object of the invention is toprovide an improved catalyst combination which has unexpected catalyticactivity for the polymerization of a-monoolefins to form crystallinehigh density polymers. Other objects will be apparent from thedescription and claims which follow.

This invention is a continuation-in-part of my copending application,Serial No. 549,860 filed November 29, 1955, now US. Patent No.2,833,755.

3,088,042 Patented May 7, 1963 The above and other objects are attainedby means of this invention, wherein a-monoolefins, either singly or inadmixture, are readily polymerized to high molecular weight solidpolymers by elfecting the polymerization in the presence of a catalyticmixture containing an aluminum dihalide having the formula R AIX whereinR is selected from the group consisting of lower alkyl radicalscontaining from 1 to 12 carbon atoms, phenyl and benzyl and the halogenatoms are selected from the group consisting of chlorine, bromine andiodine, and alkoxide of a transition metal selected from the groupconsisting of titanium, zirconium, vanadium, chromium and molybdenum,and a third component selected form the compounds having the formulas:

P(O)Y PY RC(O)Y, and YC(O)(CH C(O)Y wherein each Y is an alkylamino (NRor alkoxy (OR), said R being an alkyl radical containing 1 to 8,preferably 1 to 4 carbon atoms, and wherein n is an integer of 1 to 4.The catalytic activity of this mixture was Wholly unexpected,particularly since the monoalkyl aluminum dihalides when used alone areineffective as polymerization catalyst and when combined with certainmetal 'alkoxides produce large amounts of oils and rubbers inpolymerizing propylene and higher monoolefins. The inventive process iscarried out in liquid phase in an inert organic liquid and preferably aninert liquid hydrocarbon vehicle. The process proceeds with excellentresults over a temperature range of from 0 C. to 250 C. although it ispreferred to operate within the range of from about 50 C. to about 150C. Likewise, the reaction pressures may be varied widely from aboutatmospheric pressure to very high pressures of the order of 20,000 psi.or higher. A particular advantage of the invention is that pressures ofthe order of 30-1000 p.s.i. give excellent results, and it is notnecessary to employ the extremely high pressures which were necessaryheretofore. The liquid vehicle employed is desirably one which servesboth as a liquid reaction medium and as a solvent for the solidpolymerization products at the temperature of polymerization.

The invention is of particular importance in the preparation of highlycrystalline polypropylene, the polybutenes and polystyrene, although itcan be used for polymerizing ethylene, mixtures of ethylene andpropylene as well as other u-monoolefins containing up to 10 carbonatoms. The polyethylene which is obtained in accordance with thisinvention has a softening or fusion point greater than 120 C. wherebythe products prepared therefrom can be readily employed in contact withboiling water without deformation or other deleterious effects. Theprocess of the invention readily results in solid polymers havingmolecular Weights greater than 1000 and usually greater than 10,000.Furthermore, polymers having molecular weights of as much as 1,000,000or higher can be readily prepared if desired. The high molecular weight,high density polyethylenes of this invention are insoluble in solventsat ordinary temperatures but they are partially soluble in such solventsas xylene, toluene or tetralin at temperatures above 100 C. Thesesolubility characteristics make it possile to carry out thepolymerization process under conditions wherein the polymer formed issoluble in the reaction medium during the polymerization and can beprecipitated therefrom by lowering the temperature of the resultingmixture.

The polyethylenes of this invention are highly crystalline and usuallyexhibit crystallinity above as shown by X-ray diagrams. Ordinarily, thecrystallinities of the polyethylenes obtained by this process averageclose to In contrast to the high pressure polyethylene known heretofore,the number of methyl groups per hundred carbon atoms in thepolyethylenes of this invention are of the order of 0.5 or lower. Thedensities are of the order of 0.945 or higher, with densities of theorder of 0.96 or higher being obtained in many cases. The inherentviscosity as measured in tetralin at 145 C. can be varied from about 0.5or lower to 5.0 or higher. Melt indices as measured by the standardA.S.T.M. method may be varied from about 0.1 to 100 or even higher.

The novel catalysts described above are particularly useful forpolymerizing propylene to form a crystalline, high-density polymer. Thepolypropylene produced has a softening point above 155 C. and a densityof 0.91 and higher. Usually the density of the polypropylene is of theorder of 0.91 to 0.92.

The polyolefins prepared in accordance with the invention can be moldedor extruded and can be used to form plates, sheets, films, or a varietyof molded objects which exhibit a higher degree of stilfness than do thecorresponding high pressure polyolefins. The products can be extruded inthe form of pipe or tubing of excellent rigidity and can be injectionmolded into a great variety of articles. The polymers can also be colddrawn into ribbons, bands, fibers or filaments of high elasticity andrigidity. Fibers of high strength can be spun from the moltenpolyolefins obtained according to this process.

As has been indicated above the improved results obtained in accordancewith this invention depend upon the particular catalyst combination.Thus, one of the components of the catalyst is an aluminum dihalidehaving the formula R AlX wherein R is a hydrocarbon radical containing1-12 carbon atoms and selected from the group consisting of alkyl, aryl,and aralkyl. Among these hydrocarbon radicals are methyl, ethyl, propyl,butyl, phenyl, phenyletliyl, naphthyl, and X is a halogen selected fromthe group consisting of chlorine, bromine and iodine. The preferredalkyl aluminum dihalides are the lower alkyl derivatives, and the mostpreferred is ethyl aluminum dichloride. Another component of thecatalyst composition is an alkoxide of a transition metal selected fromthe group consisting of titanium, zirconium, vanadium, chromium andmolybdenum. In these compounds the transition metal is preferably at itsmaximum valence, but a compound of a transition metal having a reducedvalence can be used. For most desirable results it is preferred to usean alkoxide of titanium, for example, titanium ethoxide and titaniumbutoxide, and the titanium tetraalkoxides are usually used. It will beunderstood that the alkoxides of the other transition metals can be usedif desired. The third component of the catflyst composition is acompound having the formula Each Y represents a lower alkylarnino orlower alkoxy radical, R is a lower alkyl radical containing 1 to 8carbon atoms and n is an integer of 1 to 4.

Among the specific compounds that can be used are tris-N,N-dimethylphosphoramide, triethyl phosphate, mixed phosphate ester-amides,triethyl phosphite, N,N- dimethylacetamide, adipamide and the like. Thecatalyst compositions of this invention when reacted with water do notproduce hydrogen.

The limiting factor in the temperature of the process appears to be thedecomposition temperature of the catalyst. Ordinarily temperatures from50 C. to 150 C. are employed, although temperatures as low as C. or ashigh as 250 C. can be employed if desired. Usually, it is not desirableor economical to effect the polymerization at temperatures below 0 C.,and the process can be readily controlled at room temperature or higherwhich is an advantage from the standpoint of commercial processing. Thepressure employed is usually only sufficient to maintain the reactionmixture in liquid form during the polymerization, although higherpressures can be used if desired. The pressure is ordinarily achieved bypressuring the system with the monomer whereby ad ditional monomerdissolves in the reaction vehicle as the: polymerization progresses.

The polymerization embodying the invention can be carried out'ba-tchwise or in a continuous flowing stream: process. The continuousprocesses are preferred for" economic reasons, and particularly goodresults are obtained using continuous processes wherein a polymerization mixture of constant composition is continuously and. progressivelyintroduced into the polymerization zone: and the mixture resulting fromthe polymerization iscontinuously and progressively withdrawn from thepolymerization zone at an equivalent rate, whereby the relativeconcentration of the various components in the: polymerization zoneremains substantially unchanged during the process. This results information of polymersof extremely uniform molecular weight distributionover a relatively narrow range. Such uniform polymers pos sess distinctadvantages since they do not contain any substantial amount of the lowmolecular weight or high molecular weight formations which areordinarily found in polymers prepared by batch reactions.

In the continuous flowing stream process, the temperature is desirablymaintained at a substantially constant value within the preferred rangein order to achieve the highest degree of uniformity. Since it isdesirable to employ a solution of the monomer of relatively highconcentration, the process is desirably effected under a pressure offrom 30 to 1000 p.s.i. obtained by pressuring the system with themonomer being polymerized. The amount of vehicle employed can be variedover rather wide limits with relation to the monomer and catalystmixture. Best results are obtained using a concentration of catalyst offrom about 0.1% to about 2% by weight based on the weight of thevehicle. The concentration of the monomer in the vehicle will varyrather widely depending upon the reaction conditions and will usuallyrange from about 2 to 50% by weight. For a solution type of process itis preferred to use a concentration from about 2 to about 10% by weightbased on the weight of the vehicle, and for a slurry type of processhigher concentrations, for example, up to 40% and higher are preferred.Higher concentrations of monomer ordinarily increase the rate ofpolymerization, but concentrations above 5-10% by weight in a solutionprocess are ordinarily less desirable because the polymer dissolved inthe reaction medium results in a very viscous solution.

The molar ratio of aluminum dihalide to transition metal compound can bevaried within the range of 1:05 to 1:2, and the molar ratio of aluminumcompound to the third component of the catalytic mixture can be variedwithin the range of 1:1 to 1:025. A particularly effective catalystcontains one mole of transistion metal compound and 0.5 mole of thethird component per mole of aluminum compound, but it will be understoodthat higher and lower molar ratios are within the scope of invention.The polymerization time can be varied as desired and will usually be ofthe order of from 30 minutes to several hours in batch processes.Contact times of from 1 to 4 hours are commonly employed in autoclavetype reactions. When a continuous process is: employed, the contact timein the polymerization zone can also be regulated as desired, and in somecases it is not necessary to employ reaction or contact times muchbeyond one-half to one hour since a cyclic system can be employed byprecipitation of the polymer and return of the vehicle and unusedcatalyst to the charging zone wherein the catalyst can be replenishedand additional monomer introduced.

The organic vehicle employed can be an aliphatic alkane or cycloalkanesuch as pentane, hexane, heptane or cyclohexane, or a hydrogenatedaromatic compound such as tetrahydronaphthalene or decahydronaphthalene,

or a high molecular weight liquid paraffin or mixture of paraffins whichare liquid at the reaction temperature, or an aromatic hydrocarbon suchas benzene, toluene, xylene, or the like, or a halogenated aromaticcompound such as chlorobenzene, chloronaphthalene, ororthodichloro'benzene. The nature of the vehicle is subject toconsiderable variation, although the vehicle employed should be liquidunder the conditions of reaction and relatively inert. The hydrocarbonliquids are desirably employed. Other solvents which can be used includeethyl benzene, isopropyl benzene, ethyl toluene, n-propyl benzene,diethyl benzenes, mono and dialkyl naphthalene, n-pentane, n-octane,isooctane, methyl cyclohexane, tetralin, decalin, and any of the otherwellknown inert liquid hydrocarbons. The diluents employed in practicingthis invention can be advantageously purified prior to use in thepolymerization reaction by contacting the diluent, for example, in adistillation procedure or otherwise, with the polymerization catalyst toremove undesirable trace impurities. Also, prior to such purification ofthe diluent the catalyst can be contacted advantageously withpolymerizable a-monoolefin.

The polymerization ordinarily is accomplished by merely admixing thecomponents of the polymerization mixture, and no additional heat isnecessary unless it is desired to effect the polymerization at anelevated temperature in order to increase the solubility of polymericproduct in the vehicle. When the highly uniform polymers are desiredemploying the continuous process wherein the relative proportions of thevarious components are maintained substantially constant, thetemperature is desirably controlled within a relatively narrow range.This is readily accomplished since the solvent vehicle forms a highpercentage of the polymerization mixture and hence can be heated orcooled to maintain the temperature as desired.

A particularly eifective catalyst for polymerizing ethylene, propylene,styrene and other oc-monoolefins in accordance with this invention is amixture of ethyl alumnum dichloride, titanium tetrabutoxide andtris-N,N- dimethyl phosphoramide. The importance of the variouscomponents of this reaction mixture is evident from the fact that amixture of ethyl aluminum dichloride and titanium tetrabutoxide produceslarge amounts of oils and rubbers in a propylene polymerization.However, when the above phosphoramide or other third compound Within thescope of this invention is added'to the mixture the resulting catalystcomposition is highly effective for polymerizing propylene to form ahighly crystalline high-tensity, high softening polymer Without theformation of oils and rubbers.

The invention is illustrated by the following examples of certainpreferred embodiments thereof.

Example 1 In a nitrogen-filled dry box 2 grams of catalyst was added toa 500 ml. pressure bottle containing 100 ml. of dry heptane. Thecatalyst was made up of ethyl aluminum dibromide and titaniumtetrabutoxide in a molar ratio of 1:1. The pressure bottlewas thenattached to a propylene source and the reaction mixture was agitated at70 C. and under 30 psi. of propylene pressure for 6 hours. No solidpolypropylene and little, if any, liquid polymer was formed during thistime indicating that under these conditions the catalyst mixture wasineifective. for polymerizing propylene to form a solid crystallineproduct.

Example 2 The procedure described in Example 1 was followed using 2grams of a catalyst made up of ethyl aluminum dichloride, tetradodecyltitanate and tris-N,N-dimethyl phosphoramide, P(O) [N(CH in a molarratio of 121:0.5. During the 6-hour period of agitation of the reactionmixture at 70 C. under 30 p.s.i. propylene pressure, there U was formed12.9 grams of highly crystalline polypropylene having a density of 0.921and an inherent viscosity of 3.44 in tetralin at C. The polymer wasreadily molded into a hard, clear button having a softening point of161- 165 C.

When the ethyl aluminum dichloride in the above. catalyst formulationwas replaced by phenyl aluminum dichloride, an equally efiicientcatalyst was formed, and under similar conditions the use of thiscatalyst resulted in the production of 15.1 grams of highly crystallinepolypropylene. Also, replacement of the tetra dodecyl titanate withvanadium tetraalkoxide resulted in an equally eificient catalystcomposition for polymerizing propylene.

Example 3 In a nitrogen-filled dry box a 500 ml. pressure bottle wasloaded with 100 ml. of dry heptane and 2 grams of a catalyst made up ofbenzyl aluminum dibromide and zirconium tetrabutoxide in a 1:1 molarratio. The pressure bottle was then attached to a propylene source andthe reaction mixture was agitated at 70 C. and under 30 psi. ofpropylene pressure for 6 hours. No solid propylene polymer was obtained.However, 60- grams of liquid, low-molecular weight polymers were formed.Analysis by gas chromatography indicated that this product containedpropylene dimers, trimers and tetramers.

Example 4 The process of Example 3 was followed using a 2-gram catalystcharge containing methyl aluminum dibromide, titanium tetramethoxide andtris-N,N-dimethylphosphoramide in a molar ratio of 1:1:1. A 16.7 gramyield of solid polypropylene was produced. This solid polymer wasextracted with dibutyl ether to remove a small quantity of rubberypolypropylene and then extracted with heptane to remove low-molecularweight, crystalline polypropylene. The residual 13.4 grams ofpolypropylene was highly crystalline: density 0.918, inherent viscosity2.62 and softening point 162-166 C.

Vanadium alkoxides, zirconium alkoxides, molybdenum alkoxides andchromium alkoxides, when used in place of titanium alkoxides in theabove catalyst, results in catalysts that effectively polymerizepropylene to solid crystal line polymers.

Example 5 Inside a nitrogen-filled dry box a 280 ml. stainless steelautoclave was loaded with 0.75 gram of a catalyst having a 1:1:0'.25molar ratio of ethyl aluminum dichloride, titanium triethoxide andtris-N,N-dimethyl phosphoramide. The autoclave was sealed, placed in arocker and 100 ml. (51 grams) of propylene was added. Rocking wasinitiated and the mixture was heated to 85 C. for 4 hours. A yield of47.3 grams of highly crystalline polypropylene was obtained having adensity of 0.92 and an inherent viscosity of 3.84.

Mixed amide esters such as C H OP(O) (NR triethyl phosphate, triethylphosphite, N,N-dimethylacetamide and adipamide, when used in place ofthe above phosphoramide produce desirable yields of highly crystal linepolypropylene.

Example 6 The process of Example 5 was followed using 0.1 gram ofcatalyst charge containing a 11220.25 molar ratio of ethyl aluminumdibromide, vanadium tetraethoxide and tris-N,N-dimethyl phosphoramide at85 C. to produce 9.5 grams of highly crystalline polypropylene having adensity of 0.919 and an inherent viscosity of 1.48.

Example 7 The process of Example 5 was followed using 1.5 grams ofcatalyst charge containing ethyl aluminum dichloride, titaniumtetra-Z-ethylhexoxide and tris-N,N-dimethyl phosphoramide in a molarratio of 1:0.5:0.25 and at a temperature of 55 C. A highly crystallinepolypropyl' ene was formed.

7 Example 8 The process of Example was followed using 3-methyll-buteneas the monomer at a polymerization temperature of 150 C. A 28-gram yieldof highly crystalline poly- 3-methyl-l-butene was obtained. Good yieldsof highly crystalline polymer were also obtained using 4-methyl-1-pentene, l-butene, l-pentene and vinyl-cyclohexane, allylbenzene andstyrene.

Thus, by means of this invention polyolefins such as polyethylene andpolypropylene are readily produced using a catalyst combination which,based on the knowledge of the art, would not be expected to beeffective. The polymers thus obtained can be extruded, mechanicallymilled, cast or molded as desired. The polymers can be used as blendingagents with the relatively more flexible high pressure polyethylenes togive any desired combination of properties. The polymers can also beblended with antioxidants, stabilizers, plasticizers, fillers, pigments,and the like, or mixed with other polymeric materials, waxes and thelike. In general, aside from the relatively higher values for suchproperties as softening point, density, stiffness and the like, thepolymers embodying this invention can be treated in similar manner tothose obtained by other processes.

From the detailed disclosure of this invention it is quite apparent thatin this polymerization procedure a novel catalyst, not suggested inprior art polymerization procedures, is employed. As a result of the useof this novel catalyst it is possible to produce polymeric hydrocarbons,particularly polypropylene, having properties not heretofore obtainable.For example, polypropylene prepared in the presence of catalystcombinations within the scope of this invention is substantially free ofrubbery and oily polymers and thus it is not necessary to subject suchpolypropylene of this invention to extraction procedures in order toobtain a commercial product. Also polypropylene produced in accordancewith this invention possesses unexpectedly high crystallinity, anunusually high softening point and outstanding thermal stability. Suchpolyproplyene also has a very high stiffness as a result of theunexpectedly high crystallinity. The properties imparted topolypropylene prepared in accordance with this invention thuscharacterize and distinguish this polypropylene from polymers preparedby prior art polymerization procedures.

The novel catalysts defined above can be used to produce high molecularweight crystalline polymeric hydrocarbons. The molecular weight of thepolymers can be varied over a Wide range by introducing hydrogen to thepolymerization reaction. Such hydrogen can be introduced separately orin admixture with the olefin monomer. The polymers produced inaccordance with this invention can be separated from polymerizationcatalyst by suitable extraction procedures, for example, by washing withwater or lower aliphatic alcohols such as methanol.

The catalyst compositions have been described above as being effectiveprimarily for the polymerization of a-monoolefins. These catalystcompositions can, however, be used tcir polymerizing other a-olefins,and it is not necessary to limit the process of the invention tomonoolefins. Other a-olefins that can be used are butadiene, isoprene,1,3-pentadiene and the like.

Although the invention has been described in considerable detail withreference to certain preferred embodiments thereof, variations andmodifications can be efiected within the spirit and scope of thisinvention as described hereinabove and as defined in the appendedclaims.

I claim:

1. In the polymerization of a-monoolefinic hydrocarbon containing 3 to10 carbon atoms to form solid, crystalline polymer, the improvementwhich comprises catalyzing the polymerization with a catalytic mixtureconsisting essentially of an aluminum dihalide having the formula R AlXwherein R is a hydrocarbon radical containing 1 to 12 carbon atoms andselected from the group consisting of alkyl, aryl and aralkyl and thehalogen atoms being selected from the group consisting of chlorine,bromine and iodine, an alkoxide of a transition metal selected from thegroup consisting of titanium, zirconium, vanadium, chromium andmolybdenum and an organophosphorus compound selected from the groupconsisting of tri-lower alkyl phosphites, tri-lower alkyl phosphates andhexa-lower alkyl phosphoramides, the molar ratio of aluminum dihalide toorganophosphorus compound being within the range of 1: 1 to 1:025.

2. In the polymerization of propylene to form solid, crystallinepolymer, the improvement which comprises catalyzing the polymerizationwith a catalytic mixture consisting essentially of an alkyl aluminumdihalide wherein the alkyl radicals contain 1 to 12 carbon atoms and thehalogen atoms are selected from the group consisting of chlorine,bromine and iodine, a titanium alkoxide and an organophosphorus compoundselected from the group consisting of tri-lower alkyl phosphites,tri-lower alkyl phosphates and hexa-lower alkyl phosphoramides, themolar ratio of aluminum dihalide to organophosphorus compound beingwithin the range of 1:1 to 120.25.

3. In the polymerization of propylene to form solid, crystallinepolymer, the improvement which comprises effecting the polymerization inliquid dispersion in an organic liquid and in the presence of acatalytic mixture consisting essentially of a molar ratio of ethylaluminum dichloride and vanadium tetrabutoxide of 1:05 to 1:2 and amolar ratio of ethyl aluminum dichloride and tris- N, N-dimethylphosphoramide within the range of 1:1 to 1: 9.25.

4. In the polymerization of propylene to form solid, crystallinepolymer, the improvement which comprises effecting the polymerization inliquid dispersion in an organic liquid and in the presence of acatalytic mixture consisting essentially of a molar ratio of ethylaluminum dibromide and titanium tetrabutoxide of 120.5 to 1:2 and amolar ratio of ethyl aluminum dibromide and tris-N,N- dimethylphosphoramide within the range of 1:1 to 110.25.

5. In the polymerization of propylene to form solid crystalline polymerthe improvement which comprises effecting the polymerization in liquiddispersion in an organic liquid and in the presence of a catalyticmixture consisting essentially of a molar ratio of ethyl aluminumdichloride and titanium tetrabutoxide of 120.5 to 1:2 and a molar ratioof ethyl aluminum dichloride and tris- N,N-dimethyl phosphora-midewithin the range of 1:1 to 1:025.

6. In the polymerization of propylene to form solid crystalline polymerthe improvement which comprises offecting the polymerization in liquiddispersion in an inert organic liquid and in the presence of a catalyticmixture consisting essentially of a molar ratio of ethyl aluminumdichloride and titanium tetraethoxide within the range of 110.5 to 1:2and a molar ratio of ethyl aluminum dichloride to tris-N,N-dimethylphosphoramide within the range of1:1to1:0.25.

7. In the polymerization of propylene to form solid crystalline polymerthe improvement which comprises effecting the polymerization in liquiddispersion in an inert liquid hydrocarbon vehicle and in the presence ofa catalytic mixture consisting essentially of a molar ratio of ethylaluminum dichloride and titanium tetramethoxide of 1:0.5 to 1:2 and amolar ratio of ethyl aluminum dichloride and tris-N,N-dimethylphosphoramide within the range of1:1 to 1:0.25.

8. As a composition of matter, a polymerization catalyst consistingessentially of a molar ratio of ethyl aluminum dichloride and titaniumtetrabutoxide of 1:05 to 1:2 and a molar ratio of ethyl aluminumdichloride and tris- N,N-dimethyl phosphoramide within the range of 1:1to 1:0.25.

9. As a composition of matter, a polymerization catalyst consistingessentially of a molar ratio of ethyl aluminum dichloride and titaniumtetraethoxide within the range of 1:05 to 1:2 and a. molar ratio ofethyl aluminum dichloride to tris-N,N-dirnethy1 phosphoramide within therange of 1:1 to 1:025.

10. As a composition of matter, a polymerization catalyst consistingessentially of a molar ratio of ethyl aluminum dichloride and titaniumtetramethoxide of 1:0.5 to 1:2 and a molar ratio of ethyl aluminumdichloride and tris-N,N-dimethyl phosphoramide within the range of1:1to1:0.25.

11. As a composition of matter, a polymerization catalyst consistingessentially of an aluminum dihalide having the formula R AlX wherein Ris a hydrocarbon radical containing 1 to 12 carbon atoms and selectedfrom the group consisting of alkyl, aryl and aralkyl and the halogenatoms being selected from the group consisting of chlorine, bromine andiodine, an alkoxide of a transition metal selected from the groupconsisting of titanium, zirconium, vanadium, chromium and molybdenum,and an organophosphorus compound selected from the group consisting oftri-lower alkyl phosphites, tri-lower alkyl phosphates and hexa-loweralkyl phosphoramides, the molar ratio of aluminum dihalide toorganophosphorus compound being within the range of 1:1 to 1:025.

12. As a composition of matter, a polymerization catalyst consistingessentially of an alkyl aluminum dihalide wherein the alkyl radicalscontain 1 to 12 carbon atoms and the halogen atoms are selected from thegroups consisting of chlorine, bromine and iodine, a titanium alkoxideand an organophosphorus compound selected from the group consisting oftri-lowcr alkyl phosphites, tri-lower alkyl phosphates and hexa-loweralkyl phosphoramides, the molar ratio of aluminum dihalide toorganophosphorus compound being within the range of 1:1 to 1:025.

13. As a composition of matter, a polymerization catalyst consistingessentially of a molar ratio of ethyl aluminum dichloride and vanadiumtetrabutoxide of 1:05 to 1 :2 and a molar ratio of ethyl aluminumdichloride and tris-N,N-dimethyl phosphoramide within the range of 1:1to 110.25.

14. As a composition of matter, a polymerization catalyst consistingessentially of a molar ratio of ethyl aluminum dibromide and titaniumtetr-abutoxide of 1:05 to 1:2 and a molar ratio of ethyl aluminumdibromide and ttris-N,N-dimethyl phosphoramide within the range of 1:1to 12025.

References Cited in the file of this patent UNITED STATES PATENTS2,824,090 Edwards et al. Feb. 18, 1958 2,833,755 Coover et a1 May 6,1958 2,840,617 Shokal June 24, 1958 2,846,427 Findlay Aug. 5, 19582,862,917 Anderson et a1 Dec. 2, 1958 2,882,264 Barnes Apr. 14, 1959

1. IN THE POLYMERIZATION OF A-MONOOLEFINIC HYDROCARBON CONTAINING 3 TO10 CARBON ATOMS TO FORM SOLID, CRYSTALLINE POLYMER, THE IMPROVEMENTWHICH COMPRISES CATALYZING THE POLYMERIZATION WITH A CATALYST MIXTURECONSISTONG ESSENTIALLY OF AN ALUMINUM DIHALIDE HAVING THE FORMULAR1ALX12 WHEREIN R1 IS A HYDROCARBON RADICAL CONTAINING 1 TO 12 CARBONATOMS AND SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL AND ARALKYLAND THE HALOGEN ATOMS BEING SELECTED FROM THE GROUP CONSISTING OFCHLORINE, BROMINE AND IODINE, AN ALKOXIDE OF A TRANSITION METAL SELECTEDFROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM, VANADIUM, CHROMIUM ANDMOLYBDENUM AND AN ORGANOPHOSPHORUS COMPOUND SELECTED FROM THE GROUPCONSISTING OF TRI-LOWER ALKYL PHOSPHITES, TRI-LOWER ALKYL PHOSPHATES ANDHEXA-LOWER ALKYL PHOSPHORAMIDES, THE MOLAR RATIO OF ALUMINUM DIHALIDE TOORGANOPHOSPHORUS COMPOUND BEING WITHIN THE RANGE OF 1:1 TO 1:0.25.